July 26, 2010 – Cataracts are changes in clarity of the natural lens inside the eye that gradually degrade visual quality.
It is not a tumour, a new growth of skin or tissue over the eye, but fogging of the lens itself. The natural lens sits behind the coloured part of the eye (iris) in the area of the pupil, and cannot be directly seen with the naked eye unless it becomes extremely cloudy.
The lens plays a crucial role in focusing unimpeded light on the retina at the back of the eye. The retina transforms light to a neurological signal that the brain interprets as vision. Significant cataracts block and distort light passing through the lens, causing visual symptoms and complaints.
Causes and Risk Factors
There are many types of cataracts. Most are caused by a change in the chemical composition of the lens resulting in a loss of transparency. These changes can be caused by:
• Injuries to the eye, certain diseases, conditions of the eye and body.
• Birth defects.
The lens is made mostly of water and protein. Specific proteins within the lens are responsible for maintaining its clarity. Over many years, the structures of these lens proteins are altered, ultimately leading to a gradual clouding of the lens.
Rarely, cataracts can be present at birth or in early childhood as a result of hereditary enzyme defects. Severe trauma to the eye, eye surgery, or intraocular inflammation can also cause cataracts to occur earlier in life.
Other factors that may lead to development of cataracts at an earlier age include:
• excessive ultraviolet-light exposure
• use of certain medications, such as oral, topical, or inhaled steroids
• Ionizing radiation exposure – airline pilots have an increased risk of nuclear cataracts compared with non-pilots, and that risk is associated with cumulative exposure to cosmic radiation.
• Long-term exposure to bright sunlight.
• Long-term use of corticosteroids – many people with asthma rely on inhaled, and sometimes oral, steroids, as do people with chronic obstructive pulmonary disease
• Exposure to lead – lifetime lead exposure may increase the risk of developing cataracts
Having cataracts can be compared to looking through the foggy windshield of a car or through the dirty lens of a camera. Cataracts may cause a variety of complaints and visual changes, including:
• Blurred vision, difficulty with glare (often with bright sun or automobile headlights while driving at night)
• Dulled colour vision.
• Increased nearsightedness accompanied by frequent changes in eyeglass prescription.
• Occasionally double vision in one eye.
Treatment of Cataracts
Cataract surgery is recommended only when vision loss interferes with normal activities such as reading or driving, or if the cataract is preventing the treatment of another problem.
The decision to perform surgery should be based on the patient’s own assessment of functional impairment combined with the results of the eye examination and measurement of visual acuity.
• Regular eye exams for cataracts & eye health
• Avoid smoking to avoid cataracts
• Eat well to prevent cataracts
• Wear UV protecting sunglasses to prevent cataracts
• Maintaining overall health to avoid cataracts
Centre for Vision Research, University of Sydney, Australia.
National Institute of Environmental Health Sciences, USA